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J. W. SEE. l SCALE EOE STEAM ENGINE INDICATORS. uN'o. 282,931. Patented Aug.7, 1883.

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STATES JAMESV. ASEE, OE HAMILTON, OHIO,` ASSIGNOR TO THE ASHOROFT MANU- FACTURING COMPANY, OE MASSACHUSETTS AND NEW YORK.

ySCALE FOR STEAM-ENGINE INDICATORS,

vSPECIIEICATION forming part of Letters Patent No. 282,931, dated August-.57, 1883.

Application lod December 18,1882. (No model.)

To ctZZ *whom it may concern/.-

ilton, Butler county, Ohio, have invented certain new and useful Improvements in Scales v for Steam-Engine Indicators, of which the following is a specication.

The object and nature of the invention will` be understood from the following description and the accompanying drawings, in which- Figure 1 illustrates a steam-engine indicator diagram, and Fig. 2 a scaling-instrument embodying my improvements.

The steam-engine indicator is a steam-press- U ure gage arranged to be attached to a steamengine and record the varying cylinder-pressure upon a paper moving coincidently with the piston. The paper is termed a card77 or diagrami and shows the changes in pressure throughout the strokes of the engine. The 2o higher the pencil-line above a zero-line the higher the pressure. The zero-line is made by the indicator when no steam is acting upon it. Each pound of pressure acting upon the indicator raises the lpencil a certain amount, 2 5 and the diagram is measured with a scale graduated into pounds. The zero-line is not such in fact. It is really the line of atmospheric pressure, and the zero-line would lie belowa distance representing the pressure of the at- 3o mosphere, which is generally taken at fourteen and seven-tenths pounds. yAny true analysis of a steam-diagram requires that the pressures be measured from the absolute zeroline; therefore the first step is to draw that line.

Fig. l of the drawings is shown a diagram taken by an indicator. c a is the atmospheric line drawn by the indicator. To draw the absolute zero-line, locate the two points b b, measured fourteen and seven-tenths-pounds below the atmospheric line. Then, with a straight edge, draw the absolute zero-line c through these points. To locate the two points b b is a delicate operation, requiring a fine-pointedv instrument and a fine eyesight to take the fine measurement from the scale. Great care is also requiredin setting the straight-edge 1 accurately to these points. Beit known that I, J AMES XV. SEE, of Ham- 'A In practice the line is seldom accurately located. The present invention combines a straight-edge and gaging-scale.

In Fig. 2 of the drawings is shown a scale with its edge g graduated into pounds. At e are width-gages, representing fourteen and seven-tenths pounds by the edgescale. In using the instrument, the back of the widthgages e is brought to correspond with the atmospheric line of the diagram, and the absolute zero-line is drawn along the edge of the scale. The instrument shown in Fig. 2 is seen t0 be prominently marked 40. 7 This indicates that the scale is adapted for drawing the absolute Zero-lines upon diagrams based upon a pressure-scale of one-fortieth of an inch to the pound. For the purpose of this invention the straight-edge feature of the scale must essentially be' combined with the widthing-gage and with the figure to designate the scale of the pressures upon which ,the Width-gage is based. -f

I' claim as my inventiony l. The improved instrument for use with steam engine indicators, consisting of a straight-edge bearing a figure designating the unit of a certain scale of..pressures, and a widthgage corresponding to fourteen and seven-tenths of the units designated by such figure, combined substantially as and for the purpose specified.

2. The improved instrument for use with steam engine indicators, consisting of a straight-edge, a figure on said straight-edge -designating the unit of a certain scale of pressures, aline of graduations of the scale of pressures designated by such figure, and a widthgage corresponding to fourteen and seven- Y tenths of the units designated by such figure, combined substantially as and for the purpose specified.

JAMES XV. SEE.

Vituesses:

JOHN R. Voons, J. XV. CORNELL. 

